Systems for transporting self-propelled vehicles along a track have heretofore been proposed in the art and are employed, for example, for automated transport of workpieces among a plurality of work stations in an automated manufacturing environment, and also in personnel rapid transit systems. It is conventional practice for control purposes to divide at least a portion of the vehicle path into a plurality of sequential zones, and to control motion of the vehicle separately in each of the sequential zones. It has likewise been proposed to convey power and motion-control signals to an electronically-driven self-propelled vehicle through a plurality of buses parallel to the vehicle track and individually engaged by brushes or wipers carried by the vehicle.
Alimanestianu U.S. Pat. No. 3,874,301 discloses a system for controlling motion of a self-propelled vehicle wherein buses carrying velocity control signals are segmented at the sequential zones and individually connected to variable frequency oscillators or controlling synchronous propulsion motors carried by the vehicles. When applied to automated production lines or other environments wherein vehicles may become stalled in any of the track zones, applications of such variable frequency oscillator principles for controlling vehicle velocity has required use of programmable controllers or the like for detecting presence of a vehicle in any of the sequential zones and controlling velocity of subsequent vehicles accordingly. Such a system is expensive to implement and requires that a multiplicity of signal conductors extend along the vehicle track for substantial distances.